The Center for Disease Control (CDC) estimates that hospital-acquired infections cost the U.S. healthcare system $4.5 billion a year, and that 80% of these infections are transmitted by direct touch. Although the simple use of soap before and after direct contact with a patient can reduce the transmission of these infections, health care workers often fail to employ this simple measure for several reasons. First, washing with soap and water takes time. Second, such washing necessitates the use of running water, sinks, paper towels and other infrastructural needs that are expensive to provide and maintain and therefore not always immediately accessible by health-care personnel. Thus, most health care workers follow the existing washing guidelines only about 50% of the time.
In response to this problem, the CDC recently issued new hand hygiene guidelines for health care workers. One recommendation is for doctors, nurses and other health care workers to use alcohol-based hand antiseptics rather than traditional water-based soaps to decontaminate their hands between contact with each patient to prevent the spread of infections. This new CDC guideline is expected to reduce the time spent to decontaminate hands and hence increase compliance among health-care workers. Moreover, the recommended alcohol-based products can be carried with the health care worker or installed in several convenient places near patient rooms. The alcohol in the lotion will kill the bacteria, and added emollients should keep the hands soft. Furthermore, the product dries on the hands, so running water, sinks, paper towels, etc. are largely unnecessary.
A product called Avagard™, made by 3M, is commercially available having a combination of emulsifiers, namely Beheneth-10, behenyl alcohol, cetylpalmitate, and diisopropyl dimer dilinoleate with 1% chlorhexidine gluconate solution and 61% ethyl alcohol (w/w).
A product called Prevacare™, made by Johnson & Johnson, is commercially available having 60% ethanol as its active ingredient, water as a vehicle, liposome-building blocks including glycerol distearate, stearate-10, cholesterol, and polysorbate 80, sodium laureth sulfate as a surfactant, propylene glycol as a moisturizer, and preservatives including diazolidinyl urea, methylparaben, and propylparaben. Prevacare-D™ is a commercially available product having 60% ethanol as its active ingredient, and also includes cyclomethicone as an emollient, polyethylene and silica as viscosity builders, mineral oil as a moisturizer/emollient, propylparaben as a preservative and fragrance.
A principal drawback with the increased use of alcohol-based products such as Avagard™, Prevacare™, or others presently available or embodied in various issued U.S. or European patents (see e.g. U.S. Pat. Nos. 3,485,915, 4,478,853, 4,956,170, 5,403,864, 5,516,510, 5,776,430, 5,885,562, 5,951,993, 6,022,551, 6,107, 261, 6,136,771, 6,204,230, 6,352,701, and European Patent Application 0604 848) is that certain ingredients in the formulations, including the alcohol itself, may cause irritation and allergic reactions on the skin. This drawback was readily apparent in a recent study of alcohol-based disinfectants among nurses, which showed that adverse reactions occurred in approximately 12% of all individuals following exposure to these products (Cimiotti et al., 2003, Am. J. Infect. Control 31:43-48.). The instant invention provides one means of overcoming this problem. Certain zinc salts may be added to alcohol-based gels, hand scrubs or other products to prevent the irritation that may otherwise be caused by the alcohol or other active or inactive ingredients that they may contain (see e.g. U.S. Pat. Nos. 5,965,610 and 5,985,918, the contents of which are incorporated by reference herein).
Transmission of infectious diseases is also a serious public health concern outside of the health care setting. For example, a growing number of infectious agents may be transmitted by sexual contact, and public health experts increasingly advocate the use of various devices or substances to reduce or prevent the transmission of infectious agents during sexual contact. Unfortunately, such devices or substances often contain irritating components or ingredients that may cause irritation or the dermis or mucous membranes, thereby actually increasing the risk of infection. For example, male or female condoms are often made from latex or other potentially irritating substances. Genital creams, lotions or ointments often contain potentially irritating microbicides, fungicides or spermicides.
In the present invention, specific combinations of two or more water-soluble organic salts of zinc have been identified that are effective in preventing irritation caused by spermicides, microbicides, and alcohol-based gels at concentrations that are low enough so that the risk of zinc toxicity, inactivation of therapeutic compounds, and dermal and/or mucosal irritation are minimized.
It is well known that zinc salts exert numerous biological effects. For example, zinc is essential for normal growth and cognitive development in mammals, and zinc deficiency has been implicated in a host of pathophysiological states in humans, including cognitive impairment, ocular dysfunction, eating disorders and immune dysfunction among many others.
Considering the myriad effects of zinc in humans, it is unlikely that a single mechanism could account for them all. However, one of the most important functions of zinc in vivo may be as a part of metalloproteins known as “zinc finger” proteins. Zinc finger proteins contain cysteine- and/or histidine-rich domains comprised of an α helix and two β strands in an antiparallel orientation that are held together electrostatically by a divalent zinc cation (Zn2+). Zinc finger domains are commonly found on proteins that bind to and interact with RNA or DNA. Because zinc finger proteins are essential regulators of cell proliferation, it is easy to understand, at least superficially, how zinc could be crucial for normal growth and cognitive development, which requires large amounts of cell growth. This same mechanism may also explain why zinc is required for normal immune function, since rapid proliferation of various cellular elements of the immune system, such as T-cells and/or B-cells, occurs in response to the presentation of foreign antigens.
Zinc may also play a less direct and less specific role in immune function and other biological processes. Proteins are comprised of linear chains of amino acids, some of which are positively-charged, some of which are negatively-charged, and some of which are neutral. When such a linear chain is allowed to move freely in three-dimensions, constrained only by the peptidic linkages between the individual amino acids, complex three-dimensional structures result. Proteins may assume unique shapes that allow them to interact with other proteins having complementary shapes, the so-called “lock-and-key” theory of protein-protein interactions. However, due to the distribution of charged amino acids, proteins may also have unique electrical configurations that can govern their interactions with other complexly-charged protein molecules. Zinc ions, by binding to negatively-charged regions exposed on the surface of proteins, may alter the charge configuration of the protein and prevent subsequent protein-protein interactions. One practical consequence of this phenomenon, for example within the context of immune function, may be the ability of zinc ions to block the binding of viruses or other pathogens to specific receptors on the cell surface, thus preventing infection.
This latter mechanism may account for the known properties of zinc salts as anti-irritants. Irritation of the skin may ensue following the binding, either specific or non-specific, or proteinaceous or non-proteinaceous compounds to the epithelial cells comprising the surface layer of the skin or mucosa. A large number of people are known to exhibit irritant dermatitis when their skin is exposed to various chemicals, antiseptics (chlorhexidine, quaternary ammonium compound and chlorinated phenols), disinfectants such as alcohol, biological fluids (urine), latex gloves etc. Zinc salts may prevent irritation by altering the charge configuration of the irritant, thereby preventing its subsequent binding to the underlying tissue.
A number of U.S. patents relate to the incorporation of zinc salts in various gel compositions to prevent irritation. For example, U.S. Pat. No. 5,708,023 discloses the use of a gel wherein zinc gluconate comprises the sole gelling agent as a method of preventing skin irritation. Antimicrobial agents may also be incorporated into these gels. However, the relatively high concentrations of zinc (10% to 50% by weight) found in these gels makes them less desirable for internal use, where the diffusion of the water-soluble zinc salt creates the potential for systemic zinc toxicity, which can be manifested as emesis, irritation and corrosion of the gastrointestinal tract, acute renal tubular necrosis and interstitial nephritis.
U.S. Pat. Nos. 5,965,610 and 6,037,386, both entitled “Composition for inactivating irritants in fluids,” also disclose compositions containing water-soluble zinc salts such as zinc gluconate, zinc acetate, zinc sulfate, zinc undecylinate and zinc salicylate for use as anti-irritants. When used at high concentrations, these zinc salts can largely prevent irritant dermatitis. Again, these compositions are less suited to internal use due to their relatively high concentrations of zinc (2% or more of zinc oxide or other zinc salts).
U.S. Pat. No. 5,985,918, entitled “Zinc-based anti-irritant creams,” relates the use of organic salts of zinc in anti-irritant creams. In the compositions disclosed in this patent, at least 1% and more preferably 5% or more of zinc salts were needed for the products to be completely effective as anti-irritants.
Apart from the potential for systemic zinc toxicity following the absorption of high concentration water-soluble zinc salts through the skin or mucosa following their use in topical creams or gels, zinc itself may be an irritant at high concentrations. Thus, there is a practical upper limit to the amount of zinc that may be contained within anti-irritant creams and lubricants, especially those designed for internal use. The existence of a practical upper limit on the amount of zinc that is desirable for incorporation into contraceptive or antiseptic creams is further evident from the fact that, through its ability to bind to and subsequently inactivate potential irritants such as the contraceptive or antiseptic agent, the inclusion of high concentrations of zinc salts in these products may render them ineffective for their intended functions.
U.S. Patent No. 5,980,477 of Kelly, entitled “Genital lubricants with zinc salts as anti-viral additives,” relates to the incorporation of water-soluble, organic salts of zinc, at concentrations ranging from 0.5%-30%, into genital lubricants or other similar products to effectuate the inactivation of HIV-1 or other viruses implicated in the spread of sexually-transmitted diseases. At the upper limit of the zinc concentration range, there may be an increased risk of zinc toxicity, as well as the potential for vaginal irritation caused by the direct irritant effects of zinc. The effectiveness of the contraceptive agents also may be compromised. Furthermore, Kelly does not appreciate or describe the beneficial anti-irritant effects of low concentrations of combinations of water-soluble, organic salts of zinc.
In the present invention, specific combinations of two or more water-soluble organic salts of zinc have been identified that are effective in preventing irritation caused by spermicides, microbicides, and alcohol-based gels at concentrations that are low enough so that the risk of zinc toxicity, inactivation of therapeutic compounds, and mucosal irritation are minimized. The incorporation of zinc salt combinations into contraceptive or antiseptic lubricants or creams will thus render these products less irritating to the underlying mucosa, and therefore better able to protect against the contraction of infectious diseases, while maintaining the effectiveness of these products for their intended use.